Kepler’s Laws and Newton’s Discovery of Universal Gravitation

Despite his flamboyant lifestyle, Tycho was a master instrument designer and perhaps the greatest observational astronomer of the pre-telescope era. With lavish funding from the King of Denmark, he designed and equipped the finest observatory of his day, Uraniborg, on an island offshore of Copenhagen. For nearly two decades, Tycho used his massive quadrants and sextants (see Figure 8.1) to chart the skies with unprecedented accuracy. After losing the King’s support, he abandoned Uraniborg and moved to Prague where he hired the young mathematician Johannes Kepler to help solve a nagging puzzle: Tycho’s precise measurements of the position of Mars, carefully catalogued for over 20 years, were in stark disagreement with the circular-orbit models of both Ptolemy and Copernicus.